Positron emission tomography in the assessment of left ventricular function in healthy rats: A comparison of four imaging methods

Objective To measure left ventricular (LV) function parameters in heart of healthy rats by three different positron emission tomography (PET) imaging techniques and by magnetic resonance imaging (MRI). Methods ECG-gated microPET examinations were obtained in seven healthy rats with 2-deoxy-2-[18F]fluoro-d-glucose (FDG) for calculation of LV-function from the blood-pool phase of the dynamic recording (FDGBP), and also from the later myocardial uptake (FDGMyo). On subsequent days, we re-measured LV-function using the novel blood-pool tracer 68Ga-albumin (AlbBP) and again by FDG (FDGMyo2) in one setting. Cine-MRI examination provided the reference standard measurement. Results The mean LV ejection fractions (LVEF) were 56 ± 3 (FDGBP), 55 ± 3 (FDGMyo), 56 ± 3 (FDGMyo2), 57 ± 3 (AlbBP), and 57 ± 2 (MRI). There were good to excellent correlations found between the LVEF-values as compared to MRI reference standard for FDGBP (r = 0.71), FDGMyo (r = 0.86) and AlbBP (r = 0.88). Both of the blood-pool methods significantly overestimated the magnitudes of end-diastolic-volume and end-systolic-volume, whereas FDGMyo matched closely to the MRI reference standard. There was no significant bias for both blood-pool methods and a minor negative bias for FDGMyo regarding the LV ejection fraction (LVEF) when compared to cine-MRI results. There was no significant difference between the means of FDGMyo and FDGMyo2 (P = .50). Conclusions Relative to reference standard MRI measurements of LVEF, there was excellent agreement between PET-based measurements, notably for the novel blood-pool tracer 68Ga-albumin

Left ventricular functional assessment in murine models of ischemic and dilated cardiomyopathy using [18 F]FDG-PET: comparison with cardiac MRI and monitoring erythropoietin therapy

Background We performed an initial evaluation of non-invasive ECG-gated [18 F]FDG-positron emission tomography (FDG-PET) for serial measurements of left ventricular volumes and function in murine models of dilated (DCM) and ischemic cardiomyopathy (ICM), and then tested the effect of erythropoietin (EPO) treatment on DCM mice in a preliminary FDG-PET therapy monitoring study. Methods Mice developed DCM 8 weeks after injection with Coxsackievirus B3 (CVB3), whereas ICM was induced by ligation of the left anterior descending artery. LV volumes (EDV and ESV) and the ejection fraction (LVEF) of DCM, ICM and healthy control mice were measured by FDG-PET and compared with reference standard results obtained with 1.5 T magnetic resonance imaging (MRI). In the subsequent monitoring study, LVEF of DCM mice was evaluated by FDG-PET at baseline, and after 4 weeks of treatment, with EPO or saline. Results LV volumes and the LVEF as measured by FDG-PET correlated significantly with the MRI results. These correlations were higher in healthy and DCM mice than in ICM mice, in which LVEF measurements were somewhat compromised by absence of FDG uptake in the area of infarction. LV volumes (EDV and ESV) were systematically underestimated by FDG-PET, with net bias such that LVEF measurements in both models of heart disease exceeded by 15% to 20% results obtained by MRI. In our subsequent monitoring study of DCM mice, we found a significant decrease of LVEF in the EPO group, but not in the saline-treated mice. Moreover, LVEF in the EPO and saline mice significantly correlated with histological scores of fibrosis. Conclusions LVEF estimated by ECG-gated FDG-PET significantly correlated with the reference standard MRI, most notably in healthy mice and mice with DCM. FDG-PET served for longitudinal monitoring of effects of EPO treatment in DCM mice

In Vivo Monitoring of Parathyroid Hormone Treatment after Myocardial Infarction in Mice with [68Ga]Annexin A5 and [18F]Fluorodeoxyglucose Positron Emission Tomography

[68Ga]Annexin A5 positron emission tomography (PET) reveals the externalization of phosphatidylserine as a surrogate marker for apoptosis. We tested this technique for therapy monitoring in a murine model of myocardial infarction (MI) including parathyroid hormone (PTH) treatment. MI was induced in mice, and they were assigned to the saline or the PTH group. On day 2, they received [68Ga]annexin A5 PET or histofluorescence TUNEL staining. Mice had 2-deoxy-2-[18F]fluoro-D-glucose (FDG)-PET examinations on days 6 and 30 for calculation of the left ventricular ejection fraction and infarct area. [68Ga]Annexin A5 uptake was 7.4 ± 1.3 %ID/g within the infarction for the controls and 4.5 ± 1.9 %ID/g for the PTH group (p = .013). TUNEL staining revealed significantly more apoptotic cells in the infarct area on day 2 in the controls (64 ± 9%) compared to the treatment group (52 ± 4%; p = .045). FDG-PET revealed a significant decrease in infarct size in the treatment group and an increase in the controls. Examinations of left ventricular ejection fraction on days 6 and 30 did not reveal treatment effects. [68Ga]Annexin A5 PET can detect the effects of PTH treatment as a marker of apoptosis 2 days after MI; ex vivo examination confirmed significant rescue of myocardiocytes. FDG-PET showed a small but significant reduction in infarct size but no functional improvement

Temporal changes in phosphatidylserine expression and glucose metabolism after myocardial infarction: An in vivo imaging study in mice

Positron emission tomography (PET) for in vivo monitoring of phosphatidylserine externalization and glucose metabolism can potentially provide early predictors of outcome of cardioprotective therapies after myocardial infarction. We performed serial [68Ga]annexin A5 PET (annexin-PET) and [18F]fluorodeoxyglucose PET (FDG-PET) after myocardial infarction to determine the time of peak phosphatidylserine externalization in relation to impaired glucose metabolism in infracted tissue. Annexin- and FDG-PET recordings were obtained in female (C57BL6/N) mice on days 1 to 4 after ligation of the left anterior descending (LAD) artery. [68Ga]annexin A5 uptake (%ID/g) in the LAD artery territory increased from 1.7 ± 1.1 on day 1 to 5.0 ± 3.3 on day 2 and then declined to 2.0 ± 1.4 on day 3 (p = .047 vs day 2) and 1.6 ± 1.4 on day 4 (p = .014 vs day 2). These results matched apoptosis rates as estimated by autoradiography and fluorescein staining. FDG uptake (%ID/g) declined from 28 ± 14 on day 1 to 14 ± 3.5 on day 4 (p < .0001 vs day 1). Whereas FDG-PET revealed continuous loss of cell viability after permanent LAD artery occlusion, annexin-PET indicated peak phosphatidylserine expression at day 2, which might be the optimal time point for therapy monitoring

Impact of partial volume effect correction on cerebral Beta-amyloid imaging in APP-Swe mice using [18F]-florbetaben PET

Highlights - We explored the magnitude of partial volume effects (PVE) in small animal PET. - We performed correction of PVE in longitudinal [18F]-florbetaben PET data. - Longitudinal group differences resulted higher with PVE correction. - Discrepancies with autoradiography decreased with PVE correction. - The method should increase sensitivity of longitudinal studies with treatment arms. Abstract We previously investigated the progression of β-amyloid deposition in brain of mice over-expressing amyloid-precursor protein (APP-Swe), a model of Alzheimer's disease (AD), in a longitudinal PET study with the novel β-amyloid tracer [18F]-florbetaben. There were certain discrepancies between PET and autoradiographic findings, which seemed to arise from partial volume effects (PVE). Since this phenomenon can lead to bias, most especially in the quantitation of brain microPET studies of mice, we aimed in the present study to investigate the magnitude of PVE on [18F]-florbetaben quantitation in murine brain, and to establish and validate a useful correction method (PVEC). Phantom studies with solutions of known radioactivity concentration were performed to measure the full-width-at-half-maximum (FWHM) resolution of the Siemens Inveon DPET and to validate a volume-of-interest (VOI)-based PVEC algorithm. Several VOI-brain-masks were applied to perform in vivo PVEC on [18F]-florbetaben data from C57BL/6(N = 6) mice, while uncorrected and PVE-corrected data were cross-validated with gamma counting and autoradiography. Next, PVEC was performed on longitudinal PET data set consisting of 43 PET scans in APP-Swe (13–20 months) and age-matched wild-type (WT) mice using the previously defined masks. VOI-based cortex-to-cerebellum ratios (SUVR) were compared for uncorrected and PVE-corrected results. Brains from a subset of transgenic mice were ultimately examined by autoradiography ex vivo and histochemistry in vitro as gold standard assessments, and compared to VOI-based PET results. The phantom study indicated a FWHM of 1.72 mm. Applying a VOI-brain-mask including extracerebral regions gave robust PVEC, with increased precision of the SUVR results. Cortical SUVR increased with age in APP-Swe mice compared to baseline measurements (16 months: + 5.5%, p 18F]-florbetaben uptake in aging APP-Swe mice in planned studies of disease modifying treatments on amyloidogenesis

[18F]fallypride PET measurement of striatal and extrastriatal dopamine D2/3 receptor availability in recently abstinent alcoholics

Positron emission tomography (PET) shows reduced binding of the dopamine D2/3 antagonist [11C]raclopride in striatum of withdrawn psychostimulant abusers, but not consistently in patients with alcohol dependence (AD). We make first use of the high affinity ligand [18F]fallypride to obtain serial measures of D2/3 receptor availability in striatal and extrastriatal regions of AD patients undergoing detoxification. Seventeen patients (mean age 44±5y) with AD and 14 age-matched healthy volunteers participated. Each patient underwent [18F]fallypride PET upon hospital admission, and again 1-2 weeks later; two patients achieving abstinence, and two with substantial harm reduction had additional PET follow-up at 1 year. Dynamic 180-minute PET recordings were used for volume of interest (VOI)-based and voxel-wise analysis of [18F]fallypride binding potential (BPND). Mean baseline BPND in striatum of the AD patients (15.7±3.6) was unaltered during short-term follow-up, and did not differ from that in healthy controls (16.8±3.0); however, BPND was 10-20% lower in thalamus, hippocampus, and insular and temporal cortex of the AD patients (PBPND were very small in controls, but more pronounced and widespread in the AD group. Striatal and thalamic BPND increased by 30% in four patients with long-term abstinence or reduced alcohol consumption. VOI-based [18F]fallypride PET analyses revealed group differences in D2/3 receptor availability primarily in extra-striatal regions. Age-related loss of dopamine D2/3 receptors was more pronounced in AD patients. Receptor availability was unaltered by acute withdrawal, but increased in the subgroup of patients with long-term follow-up, suggesting reversibility of receptor changes